The goal of this proposal is to improve cancer clinical trials by enhancing the effectiveness of quantitative PET/CT imaging of tumor response. This has three distinct and linked components; (1) measuring and reducing the bias and variance of multi-center quantitative PET/CT imaging measurements, (2) devising optimal PET image analysis methods appropriate for quantitative PET/CT imaging in clinical trials, and (3) developing and testing guidelines for incorporating quantitative PET/CT imaging as a biomarker and measure of response in cancer clinical trial design. Underlying themes include optimizing the clinical and biologic data that can be gleaned from imaging in the setting of cancer therapy clinical trials, matching the design of the imaging components to the phase and complexity of the cancer clinical therapy trial, and matching the imaging approach to the type of tumor and the therapeutic agent. The mechanism used in the proposal is the development and testing of methods in tandem with existing clinical cancer trials that include PET imaging. This includes imaging studies performed locally at the University of Washington, in small multi-center trials as part of a regional network directed by our cancer center, and as a participant in national multi-center trials. The focus is on early drug trials (Phase I and II studies) and imaging biomarker studies; however, the methods investigated and tools developed will be equally applicable to larger (Phase III) trials and imaging as a surrogate endpoint. The combined results from all three aims will enable clinical investigators, cooperative cancer trial groups, and pharma, to optimize the use of PET imaging in cancer clinical trials and to include considerations for quantitative PET imaging markers in choosing a study design and sample size.